Published ahead of print on December 12, 2002, doi:10.1164/rccm.200205-490OC Am. J. Respir. Crit. Care Med., Volume 167, Number 6, March 2003, 868-872 A more recent version of this article appeared on March 15, 2003
Submitted on May 30, 2002 Critical Oxygen Delivery in Conscious Septic Rats Under Stagnant or Anemic HypoxiaYoshihisa Morita1,1 AC Burton Vascular Biology Laboratory, Lawson Health Research Institute, London, ON, Canada; Critical Care, London Health Sciences Centre, London, ON, Canada, 2 AC Burton Vascular Biology Laboratory, Lawson Health Research Institute, London, ON, Canada; Medicine, University of Western Ontario, London, ON, Canada, 3 AC Burton Vascular Biology Laboratory, Lawson Health Research Institute, London, ON, Canada, 4 AC Burton Vascular Biology Laboratory, Lawson Health Research Institute, London, ON, Canada; Medicine, University of Western Ontario, London, ON, Canada; Critical Care, London Health Sciences Centre, London, ON, Canada, 5 AC Burton Vascular Biology Laboratory, Lawson Health Research Institute, London, ON, Canada; Physiology, University of Western Ontario, London, ON, Canada; Medicine, University of Western Ontario, London, ON, Canada * To whom correspondence should be addressed. E-mail: cmartin1{at}uwo.ca.
Although evidence shows that critical O2 delivery (QO2crit), the point at which oxygen consumption becomes limited by O2 delivery (QO2), is not affected by the method used to decrease QO2 in healthy subjects, microcirculatory injury caused by sepsis may modify QO2crit in a unique manner. We therefore designed the present study to compare QO2crit in anemic and stagnant hypoxia in conscious septic rats. Rats were randomized to control or sepsis induced by cecal ligation and perforation. Twenty-four hours later, oxygen consumption was measured using expired gas analysis whereas QO2 was calculated from standard formula. Rats were further randomized to anemic hypoxia by isovolemic hemodilution or stagnant hypoxia by stepwise inflation of a balloon-tip catheter in the right atrium. QO2crit and critical hemoglobin concentration (Hbcrit) were calculated by dual linear regression analysis. We found 1) QO2crit was not different between anemic and stagnant hypoxia in sepsis, 2) Hbcrit in anemic hypoxia was similar between sepsis and control, indicating that tolerance to acute anemia is not altered by sepsis. Further studies are needed before the clinical relevance of these conclusions can be fully understood. Key words: oxygen consumption, cardiac output, balloon catheter, isovolemic hemodilution
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